Voyage Through the Outer Solar System White Paper Status July 2009

Argo

Candice Hansen (JPL) & the Argo Science Team Argo Concept: Flyby of Neptune, Triton and a Scientifically-selected KBO • A KBO encounter explores another primitive outer solar system body – Triton / KBO comparison – Pluto / KBO comparison – Numerous potential targets • Triton and Neptune are compelling flyby targets – Dynamic worlds, rich opportunities for new science discoveries – Trajectories identified with reasonable trip times and approach velocities • The Argo Mission is feasible for New Frontiers – Key science addressed by instrument package based on New Horizons heritage – Avenues available for additional cost savings in development, operations, and launch vehicle – Mission is scoped to be accomplished within New Frontiers cost cap Example 2019 Launch Options Voyager-like flight times to Jupiter and Saturn; even faster to Neptune

Time of Flight = 9.3 yr Time of Flight = 10.2 yr Neptune flyby 2028 Neptune flyby 2029 38S Neptune periapsis 21N Neptune periapsis KBO: 2005 PS21 KBO: 2001 QS 322 Access to Kuiper Belt Objects Argo’s accessible volume is ~4000x that of New Horizons Flight time to KBO is just ~1.5 - 3 years (KBO at 35-39 AU)

New Horizons, ~0.9° with propulsive assistance

Argo without Potentially in this cone: propulsive assistance ~60° 9 KBO’s with diameter > 400 km 40 KBO’s with 200 < diam < 400 km 18 cold classical KBO’s Argo is a Multi-Disciplinary, Multi- Target Concept

Argo Mission Statement

Argo is the next step for outer solar system exploration, illuminating the genesis and evolution of the solar system by

• characterizing Kuiper Belt objects with diverse evolutionary paths ranging from captured KBO Triton to an in situ KBO, and • accomplishing ground-breaking science at Neptune by opening a window on the dynamical nature of the atmosphere, rings, and magnetic field, and laying the groundwork for future ice-giant missions. White Paper(s) Status • Argo white paper is finished – But it is currently 28 pages long • Next steps – Send current version to OPAG, SBAG • solicit endorsements – Break into smaller target-oriented white papers • New small (7-page) white papers: – Neptune, Neptune’s rings, Neptune’s magnetosphere  Outer planet panel – Triton  Outer planet satellites panel – KBOs  Primitive bodies panel • Content of each: – Overview (solar system evolution, mission concept) - same – Specific target body science - individualized – Summary table of science objectives and proposed payload - same Backup Slides Argo Science Objectives - Triton

Triton Science Objective 1: Triton has a youthful surface, substantially modified when Triton was captured by Neptune. Argo will map the side of Triton seen only at a distance by Voyager (‘terra obscura”) and more of the northern hemisphere. Near-global surface coverage will extend the post- capture cratering history and other modification of Triton’s surface. • More of Triton's northern hemisphere will be sunlit – Most of it was in seasonal darkness for Voyager

Terminator Terra incognita in 2027: 60°

Terminator in 1989 for VGR flyby: 45° Terra Terra obscura obscura Will Triton’s enigmatic plumes still be active? Argo Science Objectives - Triton Triton Science Objective 2: Triton’s climate is controlled by its nitrogen atmosphere in vapor equilibrium with surface frost. Argo will map the distribution of ices on Triton’s surface and measure the atmospheric pressure to capture another point in time for modelling climate change on an icy body • Triton's atmosphere has changed significantly since the Voyager flyby in 1989 – Nitrogen and methane ices move seasonally from hemisphere to hemisphere and the pressure of the atmosphere increases and decreases seasonally Argo Science Objectives - Neptune

Nearly all aspects of the Neptune system detectable from Earth have changed significantly since Voyager fly-by in 1989

• Neptune's atmosphere shows fundamental differences in large- scale structure – No Vgr GDS, significant atmospheric evolution on <5-yr timescale; evidence for stratospheric heating since Voyager

Neptune Measurement Goals – Small-scale cloud distribution – Atmospheric lightning – Magnetic field measurements in completely different orientation – First detailed compositional/spectral map – First detailed infrared map – Gravitational moments refined for interior models Argo Science Objectives – Neptune system

Nearly all aspects of the Neptune system detectable from Earth have changed significantly since Voyager fly-by in 1989

• The ring system has changed – Arcs evolved within <8 yrs

• Neptune’s Magnetosphere – Very complex and undetectable from Earth Notional Argo Payload Preliminary suite based on science traceability matrix

• High resolution visible camera - New Horizons (NH) or reduced Cassini heritage - Alfred McEwen • Near-Infrared spectrometer - NH heritage - Don Banfield • UV solar & stellar occ. spectrometer - reduced Cassini heritage - Amanda Hendrix • Far-infrared linear radiometer - Diviner heritage - David Paige • Magnetometer - Krishan Khurana • Charged particle spectrometer – Messenger heritage • Gimballed high-gain antenna - heritage radio science instrument

Beyond this: explore trade space for other instrumentation in terms of science, cost, power, and mass Argo: New Frontiers 4 Mission Concept

A small body explorer doing exceptional ice giant science - Fly by a Kuiper Belt Object; close flyby of Triton - Fly by Neptune - Gravity assist from Jupiter and Saturn

Key Characteristics: Focused science mission Simple mission profile Current instrument technology Current spacecraft technology Capable payload Nuclear power Past, Present, and Future of Outer Solar System Exploration 1975 1985 1995 2005 2015 2025 2035 New Horizons

Voyager 2

Voyager 1 Cassini Titan Pioneer 11 Voyager 2 Orbiter Orbiter

Pioneer 10 Voyager 1 Galileo New Juno Cassini Europa Pioneer 11 Voyager 2 Orbiter Horizons Orbiter Orbiter Past, Present, and Future of Outer Solar System Exploration 1975 1985 1995 2005 2015 2025 2035 New Horizons Argo - Kuiper Belt

Voyager 2 Argo - Neptune & Triton

Voyager 2

Argo - Saturn GA Voyager 1 Cassini Titan Pioneer 11 Voyager 2 Orbiter Orbiter

Argo - Jupiter GA Pioneer 10 Voyager 1 Galileo New Juno Cassini Europa Pioneer 11 Voyager 2 Orbiter Horizons Orbiter Flagship